KR102523009B1 - Electrically conductive adhesive - Google Patents

Abstract

[Problems to be solved] It is possible to realize a conductive adhesive having excellent embedding properties, heat resistance and adhesion.
[Solution] The conductive adhesive to be pressed contains a thermosetting resin, a conductive filler, and an organic phosphate. The thermosetting resin includes a first polymer component having an epoxy group and a second polymer component having a functional group that reacts with the epoxy group. The ratio of the conductive filler to the total solid content is 50% by mass or more. The organic phosphate is 5 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the thermosetting resin, and has an endothermic peak in differential scanning calorimetry between the lower limit and the upper limit of the press working temperature.

Description

Conductive adhesive {ELECTRICALLY CONDUCTIVE ADHESIVE}

The present disclosure relates to conductive adhesives.

In flexible printed wiring boards, many conductive adhesives are used. For example, it is known to adhere an electromagnetic wave shielding film having a shielding layer and a conductive adhesive layer to a flexible printed wiring board. In this case, the conductive adhesive is used to firmly adhere the insulating film (coverlay) provided on the surface of the flexible printed wiring board and the shielding layer, and to secure good conduction with the ground circuit exposed from the opening formed in the insulating film. It is required to do

In recent years, heat resistance is also required for conductive adhesives, and conductive adhesives in which a conductive filler is added to an epoxy resin having excellent heat resistance are often studied.

In addition, with the miniaturization of electric equipment, it is required to embed a conductive adhesive into a small opening to ensure conductivity. For this purpose, it has been studied to improve the embedding property of the conductive adhesive by changing the resin composition of the conductive adhesive or adding various additives (see Patent Document 1, for example).

International Publication No. 2014/010524

However, it is not possible to sufficiently analyze the factors that improve the embedding property, and even if the embedding property is improved in a specific composition, it is difficult to apply it when the composition is different. Conductive adhesives are required not only for embedding properties, but also for heat resistance and adhesion described above, and it is important to realize these properties in a good balance.

An object of the present disclosure is to realize a conductive adhesive having excellent embedding properties, heat resistance and adhesion.

One aspect of the conductive adhesive of the present disclosure is a conductive adhesive to be pressed, and includes a thermosetting resin, a conductive filler, and an organic phosphate, wherein the thermosetting resin includes a first polymer component having an epoxy group, an epoxy group and A second polymer component having a reactive functional group is included, the proportion of the conductive filler to the total solid content is 50% by mass or more, and the organic phosphate is 5 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the thermosetting resin. , has an endothermic peak in differential scanning calorimetry between the lower limit and the upper limit of the press working temperature.

In one aspect of the conductive adhesive, the thermosetting resin may be a polyamide-modified epoxy resin or a polyurethane-modified epoxy resin.

In one aspect of the conductive adhesive, the press working temperature may be 150°C or higher and 190°C or lower, and the endothermic peak position may be 160°C or higher and 180°C or lower.

In one aspect of the conductive adhesive, the organic phosphate may be a metal salt of phosphinic acid.

One aspect of the electromagnetic wave shielding film of the present disclosure includes a conductive adhesive layer made of the conductive adhesive of the present disclosure and an insulating protective layer.

A shielding printed wiring board of the present disclosure includes a printed wiring board having a ground circuit and an insulating film having an opening exposing the ground circuit, and the electromagnetic wave shielding film of the present disclosure, and the conductive adhesive layer is a ground circuit in the opening It is bonded to the insulating film so that it conducts with.

According to the conductive adhesive of the present disclosure, embedding properties, heat resistance and adhesion can be improved.

[Fig. 1] A cross-sectional view showing an example of an electromagnetic wave shielding film.
[Fig. 2] A cross-sectional view showing a modified example of an electromagnetic wave shielding film.
Fig. 3 is a cross-sectional view showing a shielded printed wiring board.
[ Fig. 4 ] It is a diagram showing a method for measuring connection resistance.

The conductive adhesive of this embodiment contains a thermosetting resin, a conductive filler, and an organic phosphate. The thermosetting resin includes a first polymer component having an epoxy group and a second polymer component having a functional group that reacts with the epoxy group. The ratio of the conductive filler to the total solid content is 50% by mass or more. The organic phosphate is 5 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the thermosetting resin. In addition, it has an endothermic peak in differential scanning calorimetry between the lower limit and the upper limit of the press working temperature.

<organophosphate>

In this embodiment, the organic phosphate is preferably a polyphosphate and a metal phosphinic acid salt, more preferably a metal phosphinic acid salt. As the metal salt of phosphinic acid, aluminum salts, sodium salts, potassium salts, magnesium salts, calcium salts and the like can be used, and among these, aluminum salts are preferable. Examples of polyphosphates include melamine salts, methylamine salts, ethylamine salts, diethylamine salts, triethylamine salts, ethylenediamine salts, piperazine salts, pyridine salts, triazine salts, and ammonium salts. Among them, melamine salts this is preferable

Among these organic phosphates, those having an endothermic peak in differential scanning calorimetry between the lower limit and the upper limit of the press working temperature can be used. The press working temperature is not particularly limited, but from the viewpoint of productivity, it is preferably 150°C or higher, more preferably 160°C or higher, preferably 190°C, and more preferably 180°C or lower. Therefore, it is preferable to have an endothermic peak in differential scanning calorimetry in these temperature ranges. Among them, those having an endothermic peak in the temperature range of 160°C or more and 180°C or less are more preferable. Specifically, an aluminum salt of trisdiethylphosphinic acid having an endothermic peak around 170°C or the like can be used.

And the temperature of the endothermic peak of organic phosphate can be measured by the method shown in the Example.

By including such an organic phosphate, the embedding property of the conductive adhesive can be improved. Further, from the viewpoint of improving the embedding property and keeping the connection resistance low, the amount of the organic phosphate is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and preferably 50 parts by mass or more with respect to 100 parts by mass of the thermosetting resin. It is 40 parts by mass or less, more preferably 40 parts by mass or less. Moreover, the effect of making a conductive adhesive flame retardant can also be acquired by containing organic phosphate in such an amount.

<Thermosetting resin>

In this embodiment, the thermosetting resin contains the first polymer component having an epoxy group. The first polymer component is not particularly limited as long as it is a polymer having two or more epoxy groups in one molecule, and examples thereof include bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol S type epoxy resin; spiro cyclic epoxy resins; Naphthalene type epoxy resin: Biphenyl type epoxy resin; glycidyl ether type epoxy resins such as terpene type epoxy resins, tris(glycidyloxyphenyl)methane, and tetrakis(glycidyloxyphenyl)ethane; glycidyl amine type epoxy resins such as tetraglycidyldiaminodiphenylmethane; tetrabrombisphenol A type epoxy resin; novolak-type epoxy resins such as cresol novolac-type epoxy resins, phenol novolac-type epoxy resins, α-naphthol novolak-type epoxy resins, and brominated phenol novolak-type epoxy resins; A rubber-modified epoxy resin or the like can be used. These may be used individually by 1 type, and may use 2 or more types together. These epoxy resins may be solid or liquid at room temperature. With respect to the epoxy resin, “solid at room temperature” means a state without fluidity in a solvent-free state at 25° C., and “liquid at room temperature” means a state with fluidity under the same conditions. do it by doing

In this embodiment, the 2nd polymer component has two or more functional groups reacting with the epoxy group of the 1st polymer component in 1 molecule. For example, it can be set as a polymer which has a hydroxyl group, a carboxyl group, an epoxy group, an amino group, etc.

The second polymer component can be, for example, urethane-modified polyester having a carboxyl group. Urethane-modified polyester is polyester containing a urethane resin as a copolymer component. Urethane-modified polyester can be obtained, for example, by condensation polymerization of an acid component such as polycarboxylic acid or an anhydride thereof and a glycol component to obtain polyester, and then reacting the terminal hydroxyl group of the polyester with an isocyanate component. . Moreover, urethane-modified polyester can also be obtained by simultaneously reacting an acid component, a glycol component, and an isocyanate component.

The acid component is not particularly limited, and examples thereof include terephthalic acid, isophthalic acid, orthophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 2, 2'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, adipic acid, azelaic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid , 1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, dimer acid, trimellitic anhydride, pyromellitic anhydride, 5-(2,5-dioxotetrahydro- 3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic acid anhydride and the like can be used.

The glycol component is not particularly limited, and examples thereof include ethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, and 1,4-propanediol. -Butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 2,2,4-trimethyl-1, 5-pentanediol, cyclohexanedimethanol, neopentylhydroxypivalate ester, ethylene oxide adduct and propylene oxide adduct of bisphenol A, ethylene oxide adduct and propylene oxide adduct of hydrogenated bisphenol A, 1,9-nonane Divalent diol, 2-methyloctanediol, 1,10-decanediol, 2-butyl-2-ethyl-1,3-propanediol, tricyclodecanedimethylethanol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. Alcohol, or trihydric or higher polyhydric alcohols such as trimethylolpropane, trimethylolethane, and pentaerythritol can be used as needed.

The isocyanate component is not particularly limited, and examples thereof include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, p-phenylene diisocyanate, diphenylmethane diisocyanate, m-phenylene diisocyanate, hexamethylene diisocyanate, Tetramethylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 2,6-naphthalene diisocyanate, 3,3'-dimethyl-4,4' -Diisocyanate, 4,4'-diisocyanate diphenyl ether, 1,5-xylylene diisocyanate, 1,3-diisocyanate methylcyclohexane, 1,4-diisocyanate methylcyclohexane, isophorone diisocyanate, etc. can be used

Further, the second polymer component may be a carboxyl group-modified polyamide. The carboxyl group-modified polyamide resin is synthesized by a condensation reaction between a polyhydric carboxylic acid component such as dicarboxylic acid, tricarboxylic acid, and tetracarboxylic dianhydride and organic diisocyanate or diamine, for example.

Examples of the polyhydric carboxylic acids include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, decanedioic acid, dodecanedioic acid, and dimer acid, isophthalic acid, terephthalic acid, phthalic acid, naphthalenedicarboxylic acid, Aromatic dicarboxylic acids such as diphenylsulfonedicarboxylic acid and oxydibenzoic acid, aromatic carboxylic acids such as trimellitic acid, pyromellitic acid, diphenylsulfonetetracarboxylic dianhydride, and benzophenonetetracarboxylic dianhydride Anhydride etc. are mentioned. And these can be used individually or in combination of 2 or more types.

Examples of the organic diisocyanates include 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,5-naphthalene diisocyanate, and 3,3'-dimethyl-4. Aromatic diisocyanates such as 4'-diphenylmethane diisocyanate, p-phenylene diisocyanate, m-xylene diisocyanate, and m-tetramethylxylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylenedi and aliphatic isocyanates such as isocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, transcyclohexane-1,4-diisocyanate, hydrogenated m-xylene diisocyanate, and lysine diisocyanate. These can be used individually or in combination of 2 or more types.

And, diamine can also be used instead of the said organic diisocyanate. Examples of the diamine include phenylenediamine, diaminodiphenylpropane, diaminodiphenylmethane, benzidine, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfide, and diaminodiphenylether. can be heard

As the second polymer component, an acid anhydride-modified polyester, an epoxy resin, or the like can also be used.

When the first polymer component is an epoxy resin and the second polymer component is a urethane-modified polyester, the urethane-modified epoxy resin can be obtained after the first polymer component and the second polymer component are reacted and cured. In addition, when polyamide is used as the second polymer component, a polyamide-modified epoxy resin can be obtained. The thermosetting resin containing the first polymer component and the second polymer component in the present disclosure includes an uncured resin including an unreacted first polymer component and a second polymer component. In addition, those in a state in which the first polymer component and the second polymer component are completely reacted and unreacted ones do not remain are also included.

The first polymer component is not particularly limited, but the number average molecular weight is preferably 500 or more, and more preferably 1000 or more, from the viewpoint of improving the bulk strength of the adhesive. Moreover, from an adhesive viewpoint, 10000 or less are preferable and, as for a number average molecular weight, 5000 or less are more preferable.

The second polymer component has a number average molecular weight (Mn) of preferably 10,000 or more, preferably 50,000 or less, and more preferably 30,000 or less, from the viewpoint of further improving the embedding property. In addition, Mn can be made into the value of styrene conversion measured by gel permeation chromatography (GPC).

The mass ratio of the first polymer component to the second polymer component is preferably 1:100 to 20:100, more preferably 3:100 to 15:100. Adhesion can be improved by making the 1st polymer component and the 2nd polymer component into such a mass ratio.

The thermosetting resin may contain a curing agent that promotes a reaction between the first polymer component and the second polymer component. As the curing agent, an imidazole-based curing agent, a phenol-based curing agent, or a cationic curing agent may be used. These may be used individually by 1 type, and may use 2 or more types together.

Examples of the imidazole-based curing agent include 2-phenyl-4,5-dihydroxymethylimidazole, 2-heptadecylimidazole, 2,4-diamino-6-(2'-undecylimidazolyl)ethyl -S-triazine, 1-cyanoethyl-2-phenylimidazole, 2-phenylimidazole, 5-cyano-2-phenylimidazole, 2,4-diamino-6-[2' -methylimidazolyl-(1')]-ethyl-S-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-methylimidazole isocyanuric acid adduct, 1-cyanoethyl-2-phenyl-4,5-di(2-cyanoethoxy)methylimidazole, etc., and compounds in which an alkyl group, an ethylcyano group, a hydroxyl group, an azine, etc. are added to the imidazole ring. can

Examples of the phenol-based curing agent include novolac phenols and naphthol-based compounds.

Examples of the cationic curing agent include an amine salt of boron trifluoride, an antimony pentachloride-acetyl chloride complex, and a sulfonium salt having a phenethyl group or an allyl group.

The curing agent does not need to be blended, but from the viewpoint of accelerating the reaction, it is preferably 0.3 parts by mass or more, more preferably 1 part by mass or more, preferably 20 parts by mass or less, more preferably 20 parts by mass or less, relative to 100 parts by mass of the first polymer component. Preferably it is 15 parts by mass or less.

<Conductive filler>

Although the conductive filler is not particularly limited, for example, metal fillers, metal-coated resin fillers, carbon fillers, and mixtures thereof can be used. Examples of the metal filler include copper powder, silver powder, nickel powder, silver-coated copper powder, gold-coated copper powder, silver-coated nickel powder, and gold-coated nickel powder. These metals can be produced by an electrolytic method, an atomization method, or a reduction method. Especially, any one of silver powder, silver-coated copper powder, and copper powder is preferable.

The conductive filler is not particularly limited, but the average particle diameter is preferably 1 μm or more, more preferably 3 μm or more, preferably 50 μm or less, and more preferably 40 μm or less, from the viewpoint of contact between the fillers. . The shape of the conductive filler is not particularly limited, and may be spherical, flake, resin, or fibrous, but is preferably resin from the viewpoint of obtaining a good connection resistance value.

The content of the conductive filler can be appropriately selected depending on the application, but in order to realize isotropic conductivity, the ratio to the total solid content is 50% by mass or more, preferably 60% by mass or more, preferably 95% by mass or less, more preferably is 90% by mass or less.

<Optional ingredients>

An antifoaming agent, an antioxidant, a viscosity modifier, a diluent, an antisettling agent, a leveling agent, a coupling agent, a colorant, a flame retardant, and the like can be added to the conductive adhesive of the present embodiment as optional components.

The conductive adhesive of this embodiment can be made isotropically conductive. The conductive adhesive of the present disclosure can be used for an electromagnetic wave shielding film 101 having an insulating protective layer 112 and a conductive adhesive layer 111 as shown in FIG. 1 . Such an electromagnetic wave shielding film can make the conductive adhesive layer 111 function as a shield. And, as shown in FIG. 2 , a separate shielding layer 113 may be provided between the insulating protective layer 112 and the conductive adhesive layer 111 .

The conductive adhesive layer 111 can be formed, for example, by applying the conductive adhesive of the present embodiment onto the insulating protective layer 112 or the shielding layer 113 formed on the insulating protective layer 112 .

The thickness of the conductive adhesive layer 111 is preferably 1 μm to 50 μm from the viewpoint of controlling the embedding property.

And you may paste a peelable protective film on the surface of the conductive adhesive layer 111 as needed.

The insulating protective layer 112 is not particularly limited as long as it has sufficient insulation and can protect the conductive adhesive layer 111 and, if necessary, the shielding layer 113. For example, a thermoplastic resin composition, a thermosetting resin composition, or An active energy ray-curable composition or the like can be used.

The thermoplastic resin composition is not particularly limited, but a styrene-based resin composition, a vinyl acetate-based resin composition, a polyester-based resin composition, a polyethylene-based resin composition, a polypropylene-based resin composition, an imide-based resin composition, an acrylic resin composition, or the like can be used. there is. Although it does not specifically limit as a thermosetting resin composition, A phenol type resin composition, an epoxy type resin composition, a urethane type resin composition, a melamine type resin composition, or an alkyd type resin composition etc. can be used. Although it does not specifically limit as an active energy ray-curable composition, For example, the polymeric compound etc. which have at least 2 (meth)acryloyloxy group in a molecule|numerator can be used. The protective layer may be formed of a single material, or may be formed of two or more types of materials.

The insulating protective layer 112 may be a laminate of two or more layers different in material or physical properties such as hardness or modulus of elasticity. For example, if a laminate is made of an outer layer with low hardness and an inner layer with high hardness, the outer layer has a cushioning effect, so that in the step of heating and pressing the electromagnetic wave shielding film 101 to the printed wiring board, the shielding layer 113 pressure can be relieved. Therefore, destruction of the shielding layer 113 due to the step formed on the printed wiring board can be suppressed.

The insulating protective layer 112 includes at least one of a curing accelerator, a tackifier, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling agent, a filler, a flame retardant, a viscosity modifier, and an antiblocking agent, as necessary. it may be

The thickness of the insulating protective layer 112 is not particularly limited and can be appropriately set as necessary, but is preferably 1 μm or more, more preferably 4 μm or more, and preferably 20 μm or less, more preferably 10 μm or less, more preferably 5 μm or less. By setting the thickness of the insulating protective layer 112 to 1 μm or more, the conductive adhesive layer 111 and the shielding layer 113 can be sufficiently protected. By setting the thickness of the insulating protective layer 112 to 20 μm or less, the flexibility of the electromagnetic wave shielding film 101 can be secured, and it becomes easy to apply the electromagnetic wave shielding film 101 to a member requiring flexibility.

In the case of providing the shielding layer 113, the shielding layer 113 can be formed of a metal foil, a deposition film, a conductive filler, or the like.

Although the metal foil is not particularly limited, it can be a foil made of any one of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium and zinc, or an alloy containing two or more.

Although the thickness of metal foil is not specifically limited, 0.5 micrometer or more is preferable and 1.0 micrometer or more is more preferable. If the thickness of the metal foil is 0.5 µm or more, when a high frequency signal of 10 MHz to 100 GHz is transmitted to the shielded printed wiring board, the amount of attenuation of the high frequency signal can be suppressed. In addition, the thickness of the metal foil is preferably 12 μm or less, more preferably 10 μm or less, and still more preferably 7 μm or less. When the thickness of the metal layer is 12 μm or less, raw material cost can be suppressed, and the judgment elongation of the shielding film becomes good.

The deposited film is not particularly limited, but may be formed by depositing nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc, or the like. For deposition, an electrolytic plating method, an electroless plating method, a sputtering method, an electron beam evaporation method, a vacuum evaporation method, a chemical vapor deposition (CVD) method, or a metal organic deposition (MOCVD) method can be used.

The deposited film is not particularly limited, but may be formed by depositing nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc, or the like. For vapor deposition, an electrolytic plating method, an electroless plating method, a sputtering method, an electron beam evaporation method, a vacuum evaporation method, a chemical vapor deposition (CVD) method, or a metal organic deposition (MOCVD) method or the like can be used.

The thickness of the deposited film is not particularly limited, but is preferably 0.05 μm or more, and more preferably 0.1 μm or more. When the thickness of the metal deposited film is 0.05 μm or more, the electromagnetic wave shielding film has excellent characteristics of shielding electromagnetic waves in the shielding printed wiring board. In addition, the thickness of the metal deposited film is preferably less than 0.5 μm, and more preferably less than 0.3 μm. When the thickness of the metal deposited film is less than 0.5 μm, the electromagnetic wave shielding film has excellent bending resistance, and it is possible to suppress breakage of the shielding layer due to steps formed on the printed wiring board.

In the case of the conductive filler, the shielding layer 113 can be formed by applying a solvent containing the conductive filler to the surface of the insulating protective layer 112 and drying it. As the conductive filler, metal fillers, metal-coated resin fillers, carbon fillers, and mixtures thereof may be used. As the metal filler, copper powder, silver powder, nickel powder, silver-coated copper powder, gold-coated copper powder, silver-coated nickel powder, gold-coated nickel powder, and the like can be used. These metal powders can be prepared by an electrolysis method, an atomization method, or a reduction method. As for the shape of metal powder, spherical shape, flake shape, fiber shape, resin shape, etc. are mentioned.

In this embodiment, the thickness of the shielding layer 113 may be appropriately selected according to the required electromagnetic wave shielding effect and repeated bending/sliding resistance, but in the case of metal foil, from the viewpoint of ensuring elongation at break, it is better to set it to 12 μm or less. desirable.

The electromagnetic wave shielding film 101 of this embodiment can be used for the shielding printed wiring board 103 as shown in FIG. As shown in FIG. 3 , the shielding printed wiring board 103 has a printed wiring board 102 and an electromagnetic wave shielding film 101 .

The printed wiring board 102 has, for example, a printed circuit including a base member 122 and a ground circuit 125 provided on the base member 122 . An insulating film 121 is attached to the base member 122 by an adhesive layer 123 . An opening exposing the ground circuit 125 is formed in the insulating film 121 . A surface layer 126 such as a plating layer may be provided on the exposed portion of the ground circuit 125 . In addition, the printed wiring board 102 may be a flexible board or a rigid board.

Such a shielded printed wiring board 103 can be manufactured as follows. First, the printed wiring board 102 and the electromagnetic wave shielding film 101 are prepared.

Next, the electromagnetic wave shielding film 101 is placed on the printed wiring board 102 so that the conductive adhesive layer 111 is positioned over the opening 128 . Then, the electromagnetic wave shielding film 101 and the printed wiring board 102 are sandwiched from the vertical direction by two heating plates (not shown) heated to a predetermined temperature (eg, 120°C), and a predetermined pressure is applied. (For example, 0.5 MPa) for a short time (for example, 5 seconds). In this way, the electromagnetic wave shielding film 101 is temporarily fixed to the printed wiring board 102 .

Subsequently, the temperature of the two heating plates is set to a predetermined press temperature (eg, 170 ° C.) higher than the temporary fixing, and a predetermined pressure (eg, 3 MPa) for a predetermined time (eg, 30 min) pressurize. In this way, the electromagnetic wave shielding film 101 can be fixed to the printed wiring board 102 . The press temperature can be selected depending on the composition of the conductive adhesive, but is preferably 150° C. or higher, more preferably 160° C. or higher, and preferably 190° C. °C or lower, more preferably 180 °C or lower.

At this time, a part of the conductive adhesive layer 111 softened by heating flows into the opening 128 by pressing. Thus, the shielding layer 113 and the ground circuit 115 are connected. In the opening 128, since a sufficient amount of the conductive adhesive layer 111 exists between the shielding layer 113 and the printed wiring board 102, the electromagnetic wave shielding film 101 and the printed wiring board 102 are sufficiently bonded with strength. In addition, since the conductive adhesive layer 111 has a high embedding property, connection stability can be ensured even when exposed to high temperatures during reflow in the component mounting process.

After that, a solder reflow process for component mounting is performed. In the reflow process, the electromagnetic wave shielding film 101 and the printed wiring board 102 are exposed to a high temperature of about 260°C. Components to be mounted are not particularly limited, and include chip components such as resistors and capacitors in addition to connectors and integrated circuits.

Since the conductive adhesive of the present embodiment has a high embedding property, even when the diameter a of the opening 128 is as small as 1 mm or less, the embedding in the opening 128 is sufficiently performed, and the electromagnetic wave shielding film 101 and the ground circuit ( 125) can be ensured.

From the viewpoint of firmly bonding the electromagnetic wave shielding film 101, the peel strength between the conductive adhesive layer 111 and the insulating film 121 is preferably higher, specifically preferably 11 N/cm or more, more preferably is 13 N/cm or more, more preferably 15 N/cm or more.

The base member 122 can be, for example, a resin film or the like, and specifically, polypropylene, crosslinked polyethylene, polyester, polybenzimidazole, polyimide, polyimideamide, polyetherimide, or polyphenylene. It can be set as the film which consists of resin, such as sulfide.

The insulating film 121 is not particularly limited, but is, for example, a resin such as polyethylene terephthalate, polypropylene, crosslinked polyethylene, polyester, polybenzimidazole, polyimide, polyimideamide, polyetherimide, polyphenylene sulfide or the like. can be formed by The thickness of the insulating film 121 is not particularly limited, but may be about 10 μm to 30 μm.

The printed circuit including the ground circuit 125 can be, for example, a copper wiring pattern formed on the base member 122 or the like. The surface layer 126 is not limited to a plating layer, and may be a layer made of copper, nickel, silver, tin, or the like. In addition, the surface layer 126 may be provided as needed, and a structure in which the surface layer 126 is not provided can also be used.

The conductive adhesive of the present embodiment is excellent in embedding property and adhesiveness, and exhibits a particularly excellent effect in bonding the electromagnetic wave shielding film 101 to the printed wiring board 102. However, it is also useful in other applications where conductive adhesives are used. For example, it can be used for the adhesive layer in a conductive reinforcing board.

[Example]

Hereinafter, the conductive adhesive of the present disclosure will be described in more detail using examples. The following examples are illustrative and are not intended to limit the present invention.

<Production of electromagnetic wave shielding film>

An epoxy-based resin was coated on the release film to a thickness of 6 μm, dried, and a protective layer was formed. Subsequently, predetermined materials were mixed and stirred using a planetary stirring/defoaming device, and the conductive adhesives of Examples 1 to 3 and Comparative Examples 1 to 4 having the compositions shown in Table 1. composition was made.

Next, an electromagnetic wave shielding film was produced by applying a pasty conductive adhesive composition onto the protective layer and drying at 100°C for 3 minutes.

<Measurement of endothermic peak>

The position of the endothermic peak of the organic phosphate was measured using a differential scanning calorimetry apparatus (DSC3500SA, manufactured by NETZSCH). The measurement conditions were a temperature range of 0°C to 300°C, a heating rate of 10°C/min, and a nitrogen atmosphere.

<Adhesion to polyimide>

Adhesion between the polyimide and the conductive adhesive was measured by a 180° peel test. Specifically, the conductive adhesive layer side of the electromagnetic wave shielding film was bonded to a polyimide film (Kapton 100EN (registered trademark) manufactured by Toray-DuPont), and adhered under conditions of temperature: 170°C, time: 3 minutes, and pressure of 2 MPa. . Subsequently, a bonding film (manufactured by Arisawa Seisakusho) was bonded to the protective layer side of the electromagnetic wave shielding film under conditions of temperature: 120°C, time: 5 seconds, and pressure of 0.5 MPa. Next, a polyimide film (Kapton 100EN (registered trademark), manufactured by Toray DuPont) was pasted on the bonding film to prepare a laminate for evaluation. And the laminated body of polyimide film/bonding film/shielding film was peeled off from the polyimide film at 50 mm/min. Table 1 shows the average values with n=5 as the number of tests.

<Production of Shielded Printed Wiring Board>

Next, the electromagnetic wave shielding films and printed wiring boards produced in each Example and Comparative Example were adhered using a press machine under conditions of temperature: 170°C, time: 3 minutes, and pressure: 2 to 3 MPa, and the shielding printed wiring board was produced.

And, as a printed wiring board, as shown in FIG. 3, a copper foil pattern 125 similar to a ground circuit is formed on a base member 122 made of a polyimide film, and an insulating adhesive layer 123 and poly A cover-lay (insulating film) 121 made of mid-film was used. A plating layer was provided as a surface layer 126 on the surface of the copper foil pattern 125 . In the cover lay 121, an opening simulating a ground connection portion having a diameter a of 0.8 mm was formed.

<Measurement of connection resistance value>

As shown in FIG. 4, using the shielded printed circuit board produced in each Example and Comparative Example, the electrical resistance value between the two copper foil patterns 125 having the surface layer 126 as a plating layer on the surface is measured by an ohmmeter 205 ), and the connection resistance between the copper foil pattern 125 and the electromagnetic wave shielding film 101 was evaluated.

(Example 1)

As the first polymer component, a solid epoxy resin (NC-3000, Nippon Kayaku Co., Ltd.) was used. As the second polymer component, a polyamide resin [a carboxyl group-modified polyamide resin having an acid value of 15 mgKOH/g (number average molecular weight: 2000, Tg: 30°C)] was used. The mass ratio of the first polymer component and the second polymer component was 10:100. As a curing agent, 6n parts by mass of 2-phenyl-1H-imidazole-4,5-dimethanol (2PHZPW, manufactured by Shikoku Kasei Kogyo Co., Ltd.) was added with respect to 100 parts by mass of the resin component.

As the organic phosphate, trisdiethylphosphinic acid aluminum salt (OP935, manufactured by Clariant Japan) having an endothermic peak at 170°C by differential scanning calorimetry was used, and it was 10 parts by mass with respect to 100 parts by mass of the resin component.

As the conductive filler, a dendrite-type silver-coated copper powder having an average particle diameter of 6 μm and a silver coverage of 8% by mass was used. The conductive filler was 150 parts by mass (60% by mass relative to the total solid content) with respect to 100 parts by mass of the resin component.

The connection resistance in case the hole diameter of the obtained conductive adhesive was 0.8 mmΦ was 350 mΩ/1 hole, and the peel strength with respect to polyimide was 19 N/cm.

(Example 2)

It was carried out similarly to Example 1 except having made 20 mass parts of organic phosphate with respect to 100 mass parts of resin components.

The connection resistance when the hole diameter of the obtained conductive adhesive was 0.8 mmφ was 375 mΩ/1 hole, and the peel strength to polyimide was 21 N/cm.

(Example 3)

The second polymer component was a polyurethane-modified polyester resin, and the mass ratio between the first polymer component and the second polymer component was 10:100. In addition, the organic phosphate was 30 parts by mass with respect to 100 parts by mass of the resin component. Other conditions were the same as in Example 1.

The connection resistance when the hole diameter of the obtained conductive adhesive was 0.8 mmφ was 385 mΩ/1 hole, and the peel strength to polyimide was 16 N/cm.

(Comparative Example 1)

It was the same as Example 1 except that organic phosphate was not added. The connection resistance when the hole diameter of the obtained conductive adhesive was 0.8 mmφ was 500 mΩ/1 hole, and the peel strength to polyimide was 17 N/cm.

(Comparative Example 2)

The second polymer component was a polyurethane-modified polyester resin, and the mass ratio between the first polymer component and the second polymer component was 10:100. Also, no organic phosphate was added. Other conditions were the same as in Example 1.

The connection resistance in case the hole diameter of the obtained conductive adhesive was 0.8 mmΦ exceeded 1000 mΩ/1 hole and could not be measured. The peel strength to polyimide was 15 N/cm.

(Comparative Example 3)

It was carried out in the same manner as in Example 1 except that 20 parts by mass of melamine cyanurate (MC-6000, manufactured by Nissan Chemical Industries, Ltd.) was added to 100 parts by mass of the resin component instead of the organic phosphate. The connection resistance in case the hole diameter of the obtained conductive adhesive was 0.8 mmΦ was 350 mΩ/1 hole, and the peel strength with respect to polyimide was 10 N/cm.

(Comparative Example 4)

It was carried out similarly to Example 1 except having changed the organic phosphate to 50 mass parts with respect to 100 mass parts of resin components.

The connection resistance in case the hole diameter of the obtained conductive adhesive was 0.8 mmΦ exceeded 1000 mΩ/1 hole and could not be measured. The peel strength to polyimide was 11 N/cm.

Table 1 summarizes the results of each Example and Comparative Example.

[Table 1]

The conductive adhesive of the present disclosure is excellent in embedding property, heat resistance and adhesion, and is useful in applications such as electromagnetic wave shielding films.

101: electromagnetic wave shielding film
102: printed wiring board
103: shielded printed wiring board
111: conductive adhesive layer
112: insulating protective layer
113: shielding layer
115: ground circuit
121: insulating film
122: base member
123: adhesive layer
125: ground circuit
126: surface layer
128: opening

Claims (6)

As a conductive adhesive to be pressed,
A thermosetting resin, a conductive filler, and an organic phosphate,
The thermosetting resin includes a first polymer component having an epoxy group and a second polymer component having a functional group reacting with the epoxy group,
The conductive filler has a ratio of 50% by mass or more to the total solid content,
The organic phosphate is 5 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the thermosetting resin, and has an endothermic peak in differential scanning calorimetry between the lower limit and the upper limit of the press working temperature,
The thermosetting resin is a polyamide-modified epoxy resin or a polyurethane-modified epoxy resin,
The organic phosphate is a metal salt of phosphinic acid, a conductive adhesive. According to claim 1,
The press working temperature is 150 ° C. or more and 190 ° C. or less, and the position of the endothermic peak is 160 ° C. or more and 180 ° C. or less, the conductive adhesive. An electromagnetic wave shielding film comprising a conductive adhesive layer comprising the conductive adhesive according to claim 1 or 2, and an insulating protective layer. A printed wiring board comprising a ground circuit and an insulating film having an opening exposing the ground circuit, and
The electromagnetic wave shielding film according to claim 3
including,
The conductive adhesive layer is adhered to the insulating film so as to conduct with the ground circuit at the opening.
Shielded printed wiring board. delete delete

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